Directional broadband coupler arrangement

ABSTRACT

The coupler arrangement has an input, a main line output and a tap output. A ferromagnetic coil has a first and second axial bore. A first winding passes through the first bore and has one end connected to the input and a second end connected to the main line output. A second winding has a first terminal connected to the input, passes through the second bore and has a second terminal connected to ground. A third winding has a first end portion connected to the tap output, passes through the second bore and has a second end portion connected to ground through a terminating resistor. A fourth winding has a first end portion connected to the tap output, passes through the first bore and has a second end portion connected to ground potential. The first and fourth windings are wound through the bore and around the outside portion of the core in a first direction, while the third and second winding are wound in the opposite direction. The first and third windings have a number of turns which is much smaller than the number of turns of the second and fourth winding.

United States Patent [1 1 Dillenberger,

[ 1 DIRECTIONAL BROADBAND COUPLER ARRANGEMENT [75] Inventor: Karl Dillenberger, Berlin, Germany. 731 Assignee: fiefiiifillkmnfimbn,

Stuttgart, Germany 22'' Filed: Dec. 11, 1972 -[21] Appl. No.: 314,275

[30] Foreign Application Priority Data Dec. 11, 1971 Germany P 21 61 620.6

[52] US. Cl. 333/10, 336/180 [51] Int. Cl. H03h 7/48 [58] Field of Search 333/6, l0, l1; 336/170, 180

[56] References Cited UNITED STATES PATENTS 3,454,905 7/1969 Winegard 333/11 X 3,596,210 7/1971 Pimentel 333/11 X 3,641,464 2/1972 Crowhurst et al. 333/10 Primary ExaminerPaul L. Gensler Att0rneyMichael S. Striker [4 Oct. 16, 1973 [57] ABSTRACT The coupler arrangement has an input, a main line output and a tap output. A ferromagnetic coil has a first and second axial bore. A first winding passes through the first bore and has one end connected to the input and a second end connected to the main line output. A second winding has a first terminal connected to the input, passes through the second bore and has a second terminal connected to ground. A third winding has a first end portion connected to the tap output, passes through the second bore and has a second end portion connected to ground through a terminating resistor. A fourth winding has a first end portion connected to the tap output, passes through the first bore and has a second end portion connected to ground potential. The first and fourth windings are wound through the bore and around the outside portion of the core in a first direction, while the third and second winding are wound in the opposite direction. The first and third windings have a number of turns which is much smaller than the number of turns of the second and fourth winding.

14 Claims, 6 Drawing F igures PATENTEDBBT 16 I915 SHEET 10F 2 l DIRECTIONAL BROADBAND COUPLER ARRANGEMENT BACKGROUND OF THE INVENTION This invention relates to directional broadband coupling arrangements which have a core of ferromagnetic material and, more specifically, have a core with two holes and are used for community antenna systems.

"More specifically, the present invention relates to a coupler arrangement wherein a high frequency line applies high frequency energy to an input of the arrangement and most of the high frequency energy is transmitted to a main line output while only a considerably smaller portion thereof is transmitted to a tap output. This arrangement differs from the arrangements normally called distributor arrangements in that the distributor arrangements distribute equal amounts of energy to a plurality of lines, while the present arrangement distributes, as mentioned above, the greatest part of the incoming energy to the main line output and only a small portion thereof to one or more tap outputs.

In such arrangements it is of course desirable to prevent coupling between the'main line output and thetap output, since such coupling could lead to unwanted interference. Conventional systems of this type make use .of two spacially separated cylindrical ferrite cores,

each having an axial bore and each carrying the necessary windings. Since the distance between the ferrite cores cannot be kept precisely constant under mass production techniques, very high variations in the electrical characteristics result. Further, the maximum achievable coupling" attenuation in the region of television frequencies (approximately 40m 800 MHZ) is limited to a value of approximately 25 to 30dB'.

In an alternate conventional embodiment of the above-described coupling arrangement, two individual lines which are mutually coupled both inductively and capacitively can be used. These lines have a preferred energy transmission in a particular direction. In such lines, the inductive and capacitive coupling must have a predetermined relationship, the lengthof the line must have a value depending on the frequency of the high frequency signals and the terminating resistance at the ends of the line must correspond to the wave impedance of the lines or cables connected thereto.

In a known direction coupler, disclosed in German Auslegeschrift- 1 ,195,827 the main line has one terminal connected to the inputs, passes through the coaxial bore of a cylindrical core, and is then connected to the main line output. The tap'line has oneterminal connected through a terminating resistor to ground, is wound through the hole and around the outside surface of the core and then has a second terminal connected to the tap output which in turn of course supplies a second load; This type of arrangement allows a coupling attenuation between the two loads of approximately 32 dB. The 32 dB value-cannot be improved upon even when a core having two parallel axial bores is used, as disclosed in German .Auslegeschrift 1,195,827. Although a number of variations of a directional coupler of this type have been developed, no substantial increase in the coupling atenuation could be attained.

Further a distributor is known (German Auslegeschrift 1,257,907) which has a primary winding and two symmetrical secondary windings, which windings may besituated on a double bore core. In this distributor, the coupling attenuation between the first and second output may reach a value of approximately 25 dB, that is a value which lies at the lower end of the previously attainable coupling attenuations.

SUMMARY OF THE INVENTION It is an object of the present invention to furnish a directional high frequency coupler arrangement which results in substantially higher coupling attenuations between the main line and the tap output or outputs and which is suitable for mass production.

The present invention is a directional broadband coupler arrangement having an input, a main line output and a tap output. It comprises ferromagnetic core means having a first and second bore. It further comprises first conducting means having a first end portion connected to said input, a determined conducting portion passing through said first bore and a second end portion connected to said main line output. Second conducting means have a first end portion connected to said input, a determined conducting portion passing through said second bore and a second end portion connected to ground potential. Third conducting means have a first end portion connected to the tap I together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a coupler arrangement for a community antenna system;

FIG. 2 shows the basic arrangement of a coupler having a two-bore core;

FIG. 3a is the circuit diagram for the embodiment of the coupler system shown in FIG. 3b;

FIG. 3b is a perspective view of a coupler arrangement with approximately 10-fold amplification;

FIG. 4 is a circuit diagram showing a coupler arrangement having adjustable coupling attenuation; and

FIG. 5 is a perspective view of a coupler with an auxiliary winding, showing only the core with the auxiliary winding and an auxiliary resistor connected to said auxiliary winding.

-- DESCRIPTION OF THE'PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawing.

FIG. 1 shows the input 1 to which is connected the incoming main line. The main line output is indicated at reference numeral 2, while the tap output, to which is connected the branch line, is designated by reference numeral 3. The main high frequency energy applied to input 1 is to be transmitted to output 2, while only a small portion of said energy is to be transmitted to output 3.

Thus the coupler 4 must not only divide the high frequency energy into two unequal portions, but must also fulfill the requirement that a much higher attenuation exists between output 2 and output 3 (herein referred to as decoupling attenuation) then exists between input 1 and output 3 (herein referred to as coupling attenuation) as well as between input 1 and output 2 (herein referred to as transmission attenuation). Thus the transmission attenuation should be of the order of 0.2 to 1 dB, the coupling attenuation for example between and 20 dB, while a decoupling attenuation exceeding 40 dB is very desirable.

' A coupler arrangement in which decoupling attenuations of up to 70 dB may be attained, is built in accordance with the principal illustrated in FIG. 2.

The coupler in accordance with FIG. 2 has an unsymmetrical input 1, a main line output 2, and a tap output 3. A first conducting means 5 is connected from input 1 through first bore 6 of a ferromagnetic core 7, which has two axial bores, 6 and 8. Connected between input 1 and ground are second conducting means, a winding 9 which passes through the second bore 8 of core 7. Third conducting means, here a conductor segment 10, have an end terminal connected to the tap output 3, pass through the second bore -8 of core 7 and have a second terminal connected to ground through a terminating resistor 11. Fourth conducting means, namely a winding 23, have one end terminal connected from the tap output 3, a predetermined conducting portion passing through firstbore 6 of core 7 and a second end portion directly connected to ground potential. The resistances'shown in dashed line form in FIG. 2 signify the wave impedance of the lines connected to the various terminals.

An embodiment of a coupler which has been tested and foundsatisfactory in practice is shown in FIG. 3b

and its corresponding schematic circuit diagram in FIG. 3a. The dashed lines in FIG. 3a indicate the cross section of core 7 which has a first and second bore having reference numerals 6 and'8 respectively. It should be noted that the reference numerals used in FIG. 3a are the same as those used in FIGS. 1 and 2. The first and'third winding means 1 and 10 which are simply portions of conductor in FIG. 2 are replaced in FIGS. 3a and 3b by windings 5' and 10. It will be noted that windings 5 and 12 which are pictured as inside bore 6 in FIG. 3a are actually wound through the bore 6 and around the external surface of core 7. as shown in FIG. 3b. Similarly windings 9 and 10' are wound by passing through bore 8 and then around the outside surface of core 7. Windings 5'--and 10' have relatively few turns,

'while windings 9 and 12 have a substantially greater MHz) the permeability becomes smaller.

tional, two separate cores are used any difference in the core material in the type of the winding and unavoidable manufacturing tolerances in both electrical and the mechanical components serve to destroy the symmetry.

Further it is difficult to obtain identical mutual coupling between the two halves of a conventional broadband coupler which has been manufactured in mass production.

These difficulties are of course in part overcome by the construction of the'present coupler, which uses a single core. Further, the symmetry and a corresponding increase in the decoupling attenuation can be attained by use of an auxiliary winding which has reference numeral 13 in FIG. 4. The wire of this auxiliary winding is connected from ground, passes through the second bore 8 of core 7, thence passes around the external surface of the core between bores 6 and 8 and back through the first bore 6. At the other end of bore 6 the auxiliary winding 13 may be connected either directly to ground or, as shown in FIG. 5, may be connectedto ground through a resistor 15. Resistor 15 may serveas an adjustment resistor allowing a continuous adjustment of the coupling between windings 5', 12 and 9,10, with a consequent adjustment of the decoupling attenuation. Capacitor 16 is connected in parallel to resistor 15 in order to improve the decoupling attenuation at higher frequencies.

The construction-of the coupler may be made even more compact by inserting the terminating resistor 11 (also see FIG. 3b) into the second bore 8 of core 7 (FIG. 5). A piece of insulating hose 17 within the second bore 8 of core'7 serves to maintain the position of.

the individual windings.

Of course a similar piece of insulating hose can be inserted into bore 6.

Of course the number of turns in each winding must then have a different relationship to each other.

The directional coupler of the present invention may also be used with advantage for furnishing tap outputs from two main lines. Of course in this case further windings would be required. I

In a preferred embodiment of the present invention the core of FIG. 3b has a height of 7 mm, a width of 4 mm, a depth of 4 mm, a bore diameter of 2 mm and a distance between bore centers of 3 mm.

Windings 5i and 10 each have a half a turn, while windings 4 and 9 each have 3.5 turns.

The wave impedance at input, output, and tap are 75 ohms each, as is the resistance of resistor 11 (FIG. 3a); The transmission attenuation at 40MHz is 0.6 dB. At

' 860MHz it is 1.2 dB.

It should be noted that a high decoupling attenuation can only be attained for these broadband couplers if a...

However, in the UHF region the symmetry between the capacitive and inductive components of the coupler is very difficult to maintain. For example, if as is conven-.

revealthe gist of the present invention that others can by applying current knowledge readily adapt it for vari- I ous applications without omitting features that, from the standpoint of prior art fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended 1. A directional broadband arrangement, having a main line input, a main line output and a tap output comprising, in combination, ferromagnetic core means having a first and second hole; first conducting means having a first end portion connected to said input, a determined conducting portion extending through said first hole and a second end portion connected to said main line output; second conducting means having a first end portion connected to said input, a determined conducting portion passing through said second hole and a second end portion connected to ground; third conducting means having a first end portion connected to said tap output; a determined conducting portion passing through said second hole, and a second end portion; terminating resistor means having a first terminal connected to said second end portion of said third conducting means and a second terminal connected to ground potential; and fourth conducting means having a first end portion connected to said tap output, a determined conducting portion passing through said first hole, and a second end portion connected to ground potential.

2. An arrangement as set forth in claim 1, wherein said terminating resistor means is located in said first or said second hole of said core means.

3. An arrangement as set forth in claim 1, wherein said core means has an external surface; and wherein said second conducting means comprise second winding means wound through said second hole and around said external surface of said core means in a first predetermined winding direction; and wherein said third conducting means comprise third winding means wound through said second hole and around said external surface of said core means in said first predetermined winding direction.

4. An arrangement as set forth in claim 3, wherein said first conducting means comprise first winding means wound through said first hole and around said external surface of said core means in a second predetermined winding direction opposite to said first predetermined winding direction; and wherein said fourth conducting means comprise fourth winding means wound through said first hole and around said external surface of said core means in said second predetermined winding direction.

5. An arrangement as set forth in claim 4, wherein said first and third winding means have a predetermined number of turns; and wherein said second and fourth winding means have a number of turns greatly exceeding the number of turns of said first and third winding means.

6. An arrangement as set forth in claim 4, further comprising auxiliary winding meansfor adjusting the decoupling attenuation between said main line output and said tap output, said auxiliary winding means having a first end portion and a second end portion connected to said first end portion.

7. An arrangement as set forth in claim 4, further comprising auxiliary winding means having a first and second end portion connected in common and a predetermined conducting portion passing through said second hole, around said external surface of said core means and back through said first hole.

8. An arrangement as set forth in claim 7, wherein said core means has first and second ones of said first, second, third and fourth winding means, respectively constituting a first and second coupler arrangement; and wherein said auxiliary winding means comprise a single auxiliary winding for both said first and second coupler arrangement.

9. An arrangement as set forth in claim 7, wherein said first end portion of said auxiliary winding meansis directly connected to ground potential; further comprising auxiliary resistor means connected between said second end portion of said auxiliary winding means and ground potential.

10. An arrangement as set forth in claim 9, further comprising auxiliary capacitor means connected in parallel to said auxiliary resistor means.

11. An arrangement as set forth in claim 9, wherein said auxiliary resistor means comprise adjustable resistor means.

12. An arrangement as set forth in claim 11, wherein said adjustable-resistor means is located in said first or said second hole of said core means.

13. An arrangement as set forth in claim 1, wherein said core means comprise high permeability core means.

14. An arrangement as set forth in claim 13, wherein said core means have a permeability of 250. 

1. A directional broadband arrangement, having a main line input, a main line output and a tap output comprising, in combination, ferromagnetic core means having a first and second hole; first conducting means having a first end portion connected to said input, a determined coNducting portion extending through said first hole and a second end portion connected to said main line output; second conducting means having a first end portion connected to said input, a determined conducting portion passing through said second hole and a second end portion connected to ground; third conducting means having a first end portion connected to said tap output; a determined conducting portion passing through said second hole, and a second end portion; terminating resistor means having a first terminal connected to said second end portion of said third conducting means and a second terminal connected to ground potential; and fourth conducting means having a first end portion connected to said tap output, a determined conducting portion passing through said first hole, and a second end portion connected to ground potential.
 2. An arrangement as set forth in claim 1, wherein said terminating resistor means is located in said first or said second hole of said core means.
 3. An arrangement as set forth in claim 1, wherein said core means has an external surface; and wherein said second conducting means comprise second winding means wound through said second hole and around said external surface of said core means in a first predetermined winding direction; and wherein said third conducting means comprise third winding means wound through said second hole and around said external surface of said core means in said first predetermined winding direction.
 4. An arrangement as set forth in claim 3, wherein said first conducting means comprise first winding means wound through said first hole and around said external surface of said core means in a second predetermined winding direction opposite to said first predetermined winding direction; and wherein said fourth conducting means comprise fourth winding means wound through said first hole and around said external surface of said core means in said second predetermined winding direction.
 5. An arrangement as set forth in claim 4, wherein said first and third winding means have a predetermined number of turns; and wherein said second and fourth winding means have a number of turns greatly exceeding the number of turns of said first and third winding means.
 6. An arrangement as set forth in claim 4, further comprising auxiliary winding means for adjusting the decoupling attenuation between said main line output and said tap output, said auxiliary winding means having a first end portion and a second end portion connected to said first end portion.
 7. An arrangement as set forth in claim 4, further comprising auxiliary winding means having a first and second end portion connected in common and a predetermined conducting portion passing through said second hole, around said external surface of said core means and back through said first hole.
 8. An arrangement as set forth in claim 7, wherein said core means has first and second ones of said first, second, third and fourth winding means, respectively constituting a first and second coupler arrangement; and wherein said auxiliary winding means comprise a single auxiliary winding for both said first and second coupler arrangement.
 9. An arrangement as set forth in claim 7, wherein said first end portion of said auxiliary winding means is directly connected to ground potential; further comprising auxiliary resistor means connected between said second end portion of said auxiliary winding means and ground potential.
 10. An arrangement as set forth in claim 9, further comprising auxiliary capacitor means connected in parallel to said auxiliary resistor means.
 11. An arrangement as set forth in claim 9, wherein said auxiliary resistor means comprise adjustable resistor means.
 12. An arrangement as set forth in claim 11, wherein said adjustable resistor means is located in said first or said second hole of said core means.
 13. An arrangement as set forth in claim 1, wherein said core means comprise high permeability core meaNs.
 14. An arrangement as set forth in claim 13, wherein said core means have a permeability of
 250. 